As I’ve hinted at in previous posts, I’m thinking a lot about phytosaurs lately. These Late Triassic predators are (literally) looming large in a project I’m involved with for the day job, and I’ve had the sketchbook out in an attempt to wrap my head around the overall proportions and life appearances of these ancient archosaurs.
The first thing you tend to notice about phytosaurs is how much they look like modern crocodiles. Technically, crocs are the closest living relatives of phytosaurs, but there are so many animals between the two groups that are distinctly un-crocodile-like in overall form that their similarities are likely due to convergence more than kinship.
Still, the overall resemblance between the two groups is striking, and oftentimes crocodilians become the go-to substitutes for reconstructing phytosaurs. Some restorations are more clearly crocodile-based than others, but nearly all (mine included) show some degree of crocodilian influence. I suppose this could be considered artistic laziness (or, more charitably, artistic tradition), but I think that a distant but demonstrable relationship coupled with convergent forms and habits make a certain degree of crocodile-emulation justifiable. However, if any phytosaur-workers out there have other ideas about how these animals should look, I’d be thrilled to incorporate any comments into future restorations.
The main way that you can tell if an artist has drawn a phytosaur or crocodile is by looking for the nostrils. The nostrils of crocodiles are situated at the tip of the snout, while in phytosaurs, the nostrils are farther back, in some cases just in front of their eyes. The phytosaur at the top left of this post is Parasuchus (”near crocodile”), one of the earliest and most primitive (or, to be phylogenetically correct, least derived) forms. The nostrils of Parasuchus, while further back than any crocodile, lie further forward than they do in more advanced phytosaurs, like Angistorhinus, pictured below.
Angistorhinus (”narrow snout”) was a contemporary of Parasuchus, but was more advanced in at least two obvious respects. First, the nostrils of Angistorhinus are situated much further back on the snout, raised in a little hump just in front of its eyes. Secondly, the teeth of Angistorhinus are differentiated depending on their location in the mouth. At the front of the jaws, the teeth are large and stout, built for grabbing and crushing prey. Teeth along the main length of the jaw are small, slender cones, excellent for catching small, slippery prey and working it toward the back of the throat. At the back of the jaw (and difficult to see in this closed-mouthed view), the teeth are flattened triangular wedges, well-suited to shearing off chunks of flesh from animals too large to swallow whole. This heterodont (”different-toothed”) condition presumably helped Angistorhinus tackle a wider variety of prey than than the simpler-toothed Parasuchus.
This second sketch is the first study for a series of portraits, restoring the faces of phytosaurs known from New Mexico and the U.S. Southwest. Focusing on the heads of these animals is probably the most accurate way they can be portrayed, as North American phytosaurs are known from an abundance of well-preserved skulls but, sadly, very few examples of reconstruction-ready, articulated postcrania. These sketches will end up becoming full color paintings for an interpretive display at the day job. Throughout the process, however, I hope to share more of my preliminary drawings and sketches with readers here.
—Matt Celeskey.
File under: Reptiles, Triassic.
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